EC7: Supply
The supply of goods and services: determinants of supply, the supply curve, movements along vs shifts of the supply curve.
Supply
The supply of goods and services: determinants of supply, the supply curve, movements along vs shifts of the supply curve.
Key Fact: Supply is the quantity producers are willing and able to sell at a given price over a period of time.
Key Fact: Law of supply: as price rises, quantity supplied rises (positive relationship), shown by an upward-sloping supply curve.
Key Fact: Factors shifting supply: costs of production, technology, taxes and subsidies, number of firms, weather (agriculture).
Key Fact: Movement ALONG the curve = price change. SHIFT of the curve = non-price factor (costs, technology, etc.).
Key Fact: An increase in supply shifts right (more at every price); a decrease shifts left.
📋 Key Vocabulary and Concepts
For Supply, you must know:
- Supply
- Quantity supplied
- Law of supply
- Supply curve
- Shift in supply
- Movement along
- Cost of production
- Technology
- Subsidy
- Tax
❓ Practice Questions
Q1: Explain the difference between a movement along the supply curve and a shift of the supply curve.
Q2: Describe three factors that could cause an increase in the supply of solar panels.
Q3: Analyse how a rise in the minimum wage might affect supply of goods from labour-intensive firms.
✅ Answers
- Movement along: caused by price change only (e.g. market price rises, firms supply more). Shift: caused by non-price factor (e.g. technology reduces costs, firms supply more at every price).
- Three factors: (1) Improved technology — more efficient manufacturing reduces costs. (2) Government subsidies — reducing production costs. (3) Lower cost of raw materials (silicon). (4) More firms entering the market.
- Higher minimum wage increases labour costs for labour-intensive firms. This raises production costs, shifting supply left (less supplied at each price). The firm may raise prices, reduce output, automate, or absorb costs.
🎯 Exam Tips
- Same rule as demand: change in own price = movement; change in other factors = shift.
- Always specify shift DIRECTION: right = increase in supply, left = decrease.
- Supply shifts are usually caused by COST changes: lower costs shift right, higher costs shift left.
📝 Exam Technique
Economics Exam Tips:
When analysing supply changes, use the CSE framework: Cost factor (what changed?), Shift direction (right or left?), Effect on market (what happens to equilibrium?).
When analysing supply changes, use the CSE framework: Cost factor (what changed?), Shift direction (right or left?), Effect on market (what happens to equilibrium?).
⚠️ Common Errors
Watch Out!
Students often make mistakes here. Wrong: A subsidy always benefits consumers because it reduces the price they pay. Correct: While a subsidy lowers consumer prices, the benefits are split between consumers and producers depending on elasticity. If demand is inelastic, producers may keep most of the subsidy as higher profit. Also, consumers bear the cost through taxation.
✍️ Model Answer
Full-Mark Response
Evaluate whether government subsidies for renewable energy effectively increase green electricity supply.
A grade 9 response will: analyse how subsidies reduce costs, shifting supply right; consider effectiveness (UK renewables grew rapidly); evaluate drawbacks (cost to taxpayers, dependency risk); conclude: subsidies are effective short-to-medium term for emerging technologies, but should be phased out as renewables become cost-competitive.
📊 AO Deep Dive
Assessment Objective Focus: Supply
AO1 — Knowledge: Demonstrate knowledge of Supply with precise business/economic terminology. Define key terms and state accurate factual information.
AO2 — Application: Apply knowledge of Supply to business scenarios and case studies. Use quantitative data where relevant to support your points.
AO3 — Analysis & Evaluation: Analyse and evaluate Supply by considering trade-offs, weighing costs against benefits, and reaching a reasoned judgement. Use connectives to show chains of reasoning.
Detailed Notes: Supply
Understanding the Supply Curve and the Law of Supply
Supply is the quantity of a good or service that producers are willing and able to sell at a given price over a period of time. The law of supply states that, ceteris paribus, as the price of a good rises, the quantity supplied increases, and vice versa. This positive relationship is shown by an upward-sloping supply curve. The rationale is straightforward: higher prices mean higher potential profits, giving firms an incentive to produce more. Conversely, lower prices reduce profit margins, so firms cut production.
As with demand, it is crucial to distinguish between supply (the whole curve) and quantity supplied (a point on the curve). A change in the price of the good itself causes a movement along the supply curve; a change in any other factor causes a shift. An increase in supply means the curve shifts right (more supplied at every price); a decrease means it shifts left (less supplied at every price). This distinction is one of the most tested concepts in GCSE Economics exams.
Real-World Example
When the wholesale price of wheat fell in 2023 due to a global surplus, UK flour mills increased the quantity of wheat they were willing to buy at the lower price — this was a movement along the supply curve for wheat-based products. However, when the war in Ukraine disrupted global wheat supplies in 2022, the entire supply curve for wheat shifted left because a major producing country could not export, reducing supply at every price level.
The Conditions of Supply: Factors That Shift the Curve
Several non-price factors shift the supply curve. Changes in the costs of production are the most significant: if raw materials, wages, energy or rent increase, production becomes more expensive and supply shifts left. For UK manufacturers, energy costs are a major factor — when gas prices surged in 2022, several steel and fertiliser plants in the UK reduced output or closed temporarily because production costs exceeded the selling price. Technology improvements shift supply right by making production more efficient — for example, automated milking systems have increased the supply of UK dairy products.
Government policies also affect supply. Taxes on production (such as the Climate Change Levy on UK businesses) increase costs and shift supply left. Subsidies reduce costs and shift supply right — the UK government's subsidy for offshore wind power has dramatically increased supply, making the UK one of the world's largest offshore wind producers. External shocks like natural disasters, wars or pandemics can disrupt supply chains, shifting supply left. The number of firms in the market also matters: more firms mean greater market supply.
Real-World Example
The UK offshore wind industry demonstrates how subsidies and technology shift supply right. Government contracts for difference (CfDs) guarantee a minimum price for wind-generated electricity, encouraging investment. At the same time, larger and more efficient turbines have reduced the cost of offshore wind from around £150/MWh in 2013 to under £40/MWh by 2022. These combined factors shifted the supply curve for wind energy far to the right, with offshore wind now supplying over 10% of UK electricity.
Individual and Market Supply, and Supply Elasticity
Individual supply comes from one firm; market supply is the horizontal sum of all firms' supply at each price. Market supply depends on the number of producers and each producer's cost structure. In competitive UK markets like grocery retail, market supply is high because many firms (Tesco, Sainsbury's, Asda, Morrisons, Aldi, Lidl) each contribute to total supply. In more concentrated markets like mobile networks, only a few firms (EE, Vodafone, Three, O2) dominate supply.
Price elasticity of supply (PES) measures how responsive quantity supplied is to a price change. If PES is greater than 1, supply is elastic (responsive); if less than 1, it is inelastic (unresponsive). Supply tends to be more elastic when firms have spare capacity, can easily switch production, hold large stocks, or can quickly hire more workers. UK housing supply is famously inelastic (PES less than 0.5) because planning permission takes years, land is scarce, and construction cannot be rapidly scaled up — which explains why house prices are so volatile when demand changes.
Real-World Example
During the 2020 COVID-19 lockdown, demand for flour surged as UK consumers took up home baking. However, flour supply could not respond quickly — UK flour mills produce mainly in 16kg and 32kg bags for commercial bakeries, not 1.5kg bags for retail. Switching production lines took weeks, and with PES very inelastic in the short run, the result was empty supermarket shelves despite ample total flour supply. This demonstrates how inelastic supply creates shortages when demand suddenly increases.
Comparison: Movements vs Shifts in Supply
| Feature | Movement Along | Shift Right (Increase) | Shift Left (Decrease) |
|---|---|---|---|
| Cause | Change in price of the good itself | Favourable non-price factor | Unfavourable non-price factor |
| What changes | Quantity supplied | Supply at every price | Supply at every price |
| Profit effect | Higher price = higher profit incentive | Lower costs = higher profit at each price | Higher costs = lower profit at each price |
| UK example | Higher milk price, farms produce more | New technology increases car output | Energy crisis reduces steel output |
| Diagram | Slide along existing curve | Whole curve moves right | Whole curve moves left |
Additional Practice Questions
Q1: Explain two factors that could cause the supply curve for UK-grown vegetables to shift to the left.
Q2: Evaluate why the price elasticity of supply for housing in the UK is very inelastic, and the consequences of this for house prices.
Additional Model Answers
- Two factors that could reduce supply of UK-grown vegetables: (1) Adverse weather conditions — the 2022 UK summer drought destroyed significant potato and vegetable crops, with the Potato Council reporting yield reductions of up to 30%. This natural shock shifted the supply curve left as fewer vegetables could be produced at any given price. (2) Rising input costs — UK farmers faced increased costs for fertiliser (up over 150% in 2022 due to the war in Ukraine, since Russia is a major fertiliser exporter), diesel for tractors, and seasonal labour (wage increases and fewer EU workers post-Brexit). Higher costs mean farmers produce less at every price level, shifting the supply curve left.
- UK housing supply is highly inelastic because of several constraints: the planning permission system is slow and restrictive, with local councils able to block developments; suitable land for building is scarce, especially in high-demand areas like London and the South East; construction takes 12–18 months from permission to completion; and there is a shortage of skilled construction workers (the Construction Industry Training Board estimated a shortfall of over 250,000 workers in 2023). Additionally, housebuilders have an incentive to release new homes slowly to maintain high prices. The consequence of inelastic supply is that when demand increases — due to population growth, low interest rates, or government schemes like Help to Buy — the supply cannot respond quickly, so prices rise sharply instead. UK house prices increased by over 25% between 2020 and 2022 largely because supply could not keep up with surging demand. This inelasticity means housing affordability deteriorates, widening wealth inequality between home owners and non-owners.
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